This is for a homework assignment to make an app that calculates rental rates for vacation homes. All calculation has to be done through functions. Whenever I run the program, all the outputs return zero ($0.00). I can tell that this is because "0" is being passed to the functions instead of the value retrieved from the user input. Since the validation function was able to retrieve that input just fine, I'm at a loss as to what the problem is.
I've tried restructuring my functions from FUNCTION_NAME(PARAM1, PARAM2...) to VARIABLE = FUNCTION_NAME(PARAM1, PARAM2...), and that hasn't worked.
Private Sub btnSubmit_Click(sender As Object, e As EventArgs) Handles btnSubmit.Click
'Declare variables and constants
Dim strFirstName As String
Dim strLastName As String
Dim strPhoneNumber As String
Dim strEmailAddress As String
Dim intDaysToRent As Integer
Dim strSeason As String
Dim strBuyerState As String
Dim dblSubTotal As Double
Dim dblTaxAmount As Double
Dim dblFinalTotal As Double
Const dblOffSeason As Double = 50
Const dblPeakSeason As Double = 150
Const dblStandardSeason As Double = 100
Const dbl14DayDiscount As Double = 0.95
Const dbl30DayDiscount As Double = 0.9
Const dblTaxRate As Double = 0.1
'Validate inputs
If ValidateInputs(strFirstName, strLastName, strPhoneNumber, strEmailAddress, intDaysToRent, strSeason, strBuyerState) = True Then
'Calculate subtotal
dblSubTotal = CalculateSubTotal(intDaysToRent, strSeason, dbl14DayDiscount, dbl30DayDiscount, dblSubTotal)
'Calculate tax amount
dblTaxAmount = CalculateTaxAmount(dblSubTotal, strBuyerState, dblTaxRate, dblTaxAmount)
'Calculate final total
dblFinalTotal = CalculateFinalTotal(dblSubTotal, dblTaxAmount, dblFinalTotal)
____________________________________________________________
Function ValidateInputs(ByVal FirstName As String, ByVal LastName As String, ByVal PhoneNumber As String, ByVal EmailAddress As String, ByVal DaysToRent As Integer, ByVal Season As String, ByVal BuyerState As String)
'Main validation procedure
If ValidateFirstName(FirstName) = True Then
If ValidateLastName(LastName) = True Then
If ValidatePhoneNumber(PhoneNumber) = True Then
If ValidateEmailAddress(EmailAddress) = True Then
If ValidateDaysToRent(DaysToRent) = True Then
If ValidateSeason(Season) = True Then
If ValidateBuyerState(BuyerState) = True Then
Return True
Else Return False
End If
Else Return False
End If
Else Return False
End If
Else Return False
End If
Else Return False
End If
Else Return False
End If
Else
Return False
Exit Function
End If
End Function
____________________________________________________________
'First name validation subroutine
Function ValidateFirstName(ByRef FirstName As String) As Boolean
'Check that input exists
If txtFirstName.Text Is String.Empty Then
txtFirstName.BackColor = Color.Yellow
txtFirstName.Focus()
MessageBox.Show("Please enter the renter's first name.")
Return False
Exit Function
'Check that input is a valid string
ElseIf IsNumeric(txtFirstName.Text) Then
txtFirstName.BackColor = Color.Yellow
txtFirstName.Focus()
MessageBox.Show("Please enter letters only.")
Return False
Exit Function
Else
FirstName = txtFirstName.Text
Return True
End If
End Function
____________________________________________________________
'Last name validation subroutine
Function ValidateLastName(ByRef LastName As String) As Boolean
'Check that input exists
If txtLastName.Text Is String.Empty Then
txtLastName.BackColor = Color.Yellow
txtLastName.Focus()
MessageBox.Show("Please enter the renter's last name.")
Return False
Exit Function
'Check that input is valid string
ElseIf IsNumeric(txtLastName.Text) Then
txtLastName.BackColor = Color.Yellow
txtLastName.Focus()
MessageBox.Show("Please enter letters only.")
Return False
Exit Function
Else
LastName = txtLastName.Text
Return True
End If
End Function
____________________________________________________________
'Validate phone number subroutine
Function ValidatePhoneNumber(ByRef PhoneNumber As String) As Boolean
'Check that input exists
If txtPhoneNumber.Text Is String.Empty Then
txtPhoneNumber.BackColor = Color.Yellow
txtPhoneNumber.Focus()
MessageBox.Show("Please enter the renter's phone number.")
Return False
Exit Function
'Check that input is valid string
ElseIf IsNumeric(txtPhoneNumber.Text) Then
PhoneNumber = txtPhoneNumber.Text
Return True
Else
txtPhoneNumber.BackColor = Color.Yellow
txtPhoneNumber.Focus()
MessageBox.Show("Please enter numbers only.")
Return False
Exit Function
End If
End Function
____________________________________________________________
'Validate email address subroutine
Function ValidateEmailAddress(ByRef EmailAddress As String) As Boolean
'Check that input exists
If txtEmail.Text Is String.Empty Then
txtEmail.BackColor = Color.Yellow
txtEmail.Focus()
MessageBox.Show("Please enter the renter's email address.")
Return False
Exit Function
Else
EmailAddress = txtEmail.Text
Return True
End If
End Function
____________________________________________________________
'Validate days to rent subroutine
Function ValidateDaysToRent(ByVal DaysToRent As String) As Boolean
'Check that input exists
If txtDaysRented.Text Is String.Empty Then
txtDaysRented.BackColor = Color.Yellow
txtDaysRented.Focus()
MessageBox.Show("Please enter the number of days the condo will be rented.")
Return False
'Check that input is valid string
ElseIf IsNumeric(txtDaysRented.Text) Then
DaysToRent = txtDaysRented.Text
Return True
Else
txtDaysRented.BackColor = Color.Yellow
txtDaysRented.Focus()
MessageBox.Show("Please enter numbers only.")
Return False
Exit Function
End If
End Function
____________________________________________________________
'Season validation subroutine
Function ValidateSeason(ByVal Season As String) As Boolean
'Check that input exists
If cboSeason.Text Is String.Empty Then
cboSeason.BackColor = Color.Yellow
cboSeason.Focus()
MessageBox.Show("Please enter the season the condo will be rented in.")
Return False
Exit Function
Else
Season = cboSeason.Text
Return True
End If
End Function
____________________________________________________________
'State validation subroutine
Function ValidateBuyerState(ByVal BuyerState As String) As Boolean
'Check that input exists
If cboState.Text Is String.Empty Then
cboState.BackColor = Color.Yellow
cboState.Focus()
MessageBox.Show("Please enter the season the renter's state of residence.")
Return False
Exit Function
Else
BuyerState = cboState.Text
Return True
End If
End Function
____________________________________________________________
'Subtotal Calcultion Function
Function CalculateSubTotal(ByVal DaysToRent As Integer, ByRef Season As String, ByVal Discount14 As Double, ByVal Discount30 As Double, ByRef Subtotal As Double) As Double
'Declare variable
Dim dblSubTotal As Double
Dim dblSeasonRate As Double
Dim strSeason As String
cboSeason.Text = strSeason
'Determine season rate
If Season = "Off Season" Then
dblSeasonRate = 50
ElseIf Season = "Peak Season" Then
dblSeasonRate = 150
ElseIf Season = "Standard Season" Then
dblSeasonRate = 100
End If
'Calculate subtotal
dblSubTotal = DaysToRent * dblSeasonRate
'Calculate discount (if applicable)
If DaysToRent > 14 And DaysToRent < 31 Then
dblSubTotal = Subtotal * Discount14
ElseIf DaysToRent > 30 Then
dblSubTotal = Subtotal * Discount30
End If
Return dblSubTotal
End Function
____________________________________________________________
'Tax amount calculation function
Function CalculateTaxAmount(ByVal Subtotal As Double, ByVal State As String, ByVal TaxRate As Double, ByRef TaxAmount As Double) As Double
'Calculate tax rate
If State = "Florida" Then
TaxAmount = 0
Else
TaxAmount = Subtotal * TaxRate
End If
Return TaxAmount
End Function
____________________________________________________________
'Final total calculation function
Function CalculateFinalTotal(ByVal Subtotal As Double, ByVal TaxAmount As Double, ByRef FinalTotal As Double) As Double
'Calculate final total
FinalTotal = Subtotal + TaxAmount
Return FinalTotal
End Function
You are passing the parameters to ValidateInputs using byval. This creates a copy of these variables in the function & it is those copies that the individual validation functions assign values to. The variables in btnSubmit_Click are left as their default values & these are what are passed to the calculation functions.
Changing the parameters to use byref will stop this:
Function ValidateInputs(ByRef FirstName As String, ByRef LastName As String, ByRef PhoneNumber As String, ByRef EmailAddress As String, ByRef DaysToRent As Integer, ByRef Season As String, ByRef BuyerState As String)